Sensor control device, sensor system, and load control system

ABSTRACT

A sensor control device includes: a determiner which has a first determination mode for determining whether a person is present, based on a result of detection by a first sensor and a result of detection by a second sensor, and a second determination mode for determining whether a person is present, based on a result of detection by the second sensor, wherein the determiner suspends determination as to whether a person is present in the first determination mode, if a brightness change value indicating a change in brightness in a first detection range during a certain time period is greater than a predetermined value in the first determination mode, and determines whether a person is present in the first determination mode, if the brightness change value in the first detection range is less than the predetermined value in the first determination mode.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Japanese Patent Application Number 2015-051096 filed on Mar. 13, 2015, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a detection device, a load control device, and a load control system.

2. Description of the Related Art

Conventionally, a load control device has been used which controls a load device that is a control target, based on a result of detection by a sensor which detects whether a person is present.

As a load control device of this type, a lighting control terminal which includes an imaging element has been known (see Japanese Unexamined Patent Application Publication No. 2013-4311 (Patent Literature 1)).

The lighting control terminal disclosed in Patent Literature 1 determines whether a person is present, based on an image captured by the imaging element, to control dimming of lighting apparatuses. An image capturing range of the imaging element is determined so as to include illumination ranges of the lighting apparatuses. The lighting control terminal divides the captured image into a plurality of regions in correspondence with the illumination ranges of the lighting apparatuses. Upon the detection of a person who has entered the room from the captured image, the lighting control terminal according to Patent Literature 1 controls the dimming of a lighting apparatus for a region where the person is present.

In addition, as a configuration applicable to a load control device, a human body detecting device is known (see Japanese Unexamined Patent Application Publication No. 2001-325677 (Patent Literature 2)) which includes a human body detecting sensor which captures an image of motion of a human body and processes the image, and an infrared sensor which operates by thermal sensing.

The human body detecting device according to Patent Literature 2 includes an infrared sensor in addition to a human body detecting sensor so that the infrared sensor which performs detection at a high speed complements a delay in image processing by the human body detecting sensor, thus improving sensing performance.

SUMMARY

There is a demand for a sensor control device that has a configuration for more accurately detecting a person, and also a demand for further improvement in the configuration since the configurations of the lighting control terminal according to Patent Literature 1 and the human body detecting device according to Patent Literature 2 are insufficient.

The present disclosure provides a sensor control device which detects a person more accurately, a sensor system, and a load control system.

The sensor control device according to an aspect of the present disclosure is a sensor control device which controls: a first sensor which detects, based on a captured image, whether a person is present in a first detection range; and a second sensor which detects, based on infrared radiation, whether a person is present in a second detection range which overlaps at least a portion of the first detection range, the sensor control device including a determiner which has a first determination mode for determining whether a person is present, based on a result of detection by the first sensor and a result of detection by the second sensor, and a second determination mode for determining whether a person is present, based on a result of detection by the second sensor, wherein the determiner suspends determination as to whether a person is present in the first determination mode, if a brightness change value indicating a change in brightness in the first detection range during a certain time period is greater than a predetermined value in the first determination mode, and determines whether a person is present in the first determination mode, if the brightness change value in the first detection range is less than the predetermined value in the first determination mode.

The sensor system according to an aspect the present disclosure is a sensor system including: the sensor control device; the first sensor; and the second sensor.

The load control system according to an aspect of the present disclosure is a load control system including: the sensor control device; and a controller which controls a load, based on a result of determination by the sensor control device.

The sensor control device, the sensor system, and the load control system according to the present disclosure achieve advantageous effects of increasing the accuracy of detecting a person.

BRIEF DESCRIPTION OF DRAWINGS

The figures depict one or more implementations in accordance with the present teaching, by way of examples only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.

FIG. 1 is a perspective view illustrating a load control device according to an embodiment;

FIG. 2 is an exploded perspective view illustrating the load control device according to the embodiment;

FIG. 3 is a plan view illustrating the load control device according to the embodiment;

FIG. 4 is a block diagram illustrating the load control device according to the embodiment;

FIG. 5 is a perspective view illustrating a first detection range and a second detection range of the load control device according to the embodiment;

FIG. 6 is a detailed timing diagram illustrating operation of a determiner included in the load control device according to the embodiment;

FIG. 7 is a block diagram illustrating a load control system which includes the load control device according to the embodiment;

FIG. 8 is a flowchart illustrating an example of switching between a first determination mode and a second determination mode by the determiner according to the embodiment; and

FIG. 9 is a flowchart illustrating an example of suspending determination in the first determination mode by the determiner according to the embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following describes embodiments with reference to the drawings. The embodiments described herein are specific examples of the present disclosure. Thus, numerical values, shapes, elements, arrangement and connection of the elements, steps (processes), and the processing order of the steps described in the embodiments below are examples, and are not intended to limit the present disclosure. Among the elements in the embodiments below, an element which is not described in an independent claim can be added arbitrarily. The sizes and positional relationship of members illustrated in the drawings may be exaggerated in order to provide clear description. In the following description, with regard to the elements included in embodiments, a plurality of elements may be achieved by a single member and that member may serve as the plurality of elements, or the function of one member may be divided and achieved by a plurality of members.

The following describes load control device 10 according to the present embodiment, with reference to FIGS. 1 to 9. A description of load control system 30 which includes load control device 10 according to the present embodiment is given with reference to FIG. 7. The same numerals are given to the same components throughout the drawings, and redundant description is omitted.

Load control device 10 according to the present embodiment includes casing 1 and lid 2 as illustrated in FIGS. 1 and 2. Casing 1 has a cylindrical shape with a closed end. Lid 2 is provided so as to close opening 1 aa of casing 1. Lid 2 includes first sensor 5 and second sensors 6. First sensor 5 is provided in a center portion of lid 2 in plan view, as illustrated in FIG. 3. Second sensors 6 are provided along the circumferential portion of lid 2 in plan view. Determiner 3 and communicator 4 illustrated in FIG. 4 are housed in the inner space surrounded by casing 1 and lid 2. Determiner 3 determines whether a person is present, based on a first sensor signal from first sensor 5 and second sensor signals from second sensors 6. Communicator 4 outputs a control signal, based on the result of determination by determiner 3. First sensor 5 includes imaging element 5 a. Imaging element 5 a captures an image of first detection range 10 aa illustrated in FIG. 5. First sensor 5 detects whether a person is present in first detection range 10 aa, based on image data generated by imaging element 5 a through capturing an image of first detection range 10 aa. Second sensors 6 each include infrared sensor 6 a which may be referred to as a light receiver. Infrared sensor 6 a detects infrared radiation in second detection range 10 ba. Second sensor 6 detects whether a person is present in second detection range 10 ba, based on the infrared radiation detected by infrared sensor 6 a. First detection range 10 aa overlaps second detection ranges 10 ba of second sensors 6. Determiner 3 has a first determination mode and a second determination mode. In the first determination mode, determiner 3 determines whether a person is present, based on both a first sensor signal from first sensor 5 and a second sensor signal from second sensor 6. In the second determination mode, determiner 3 determines whether a person is present, based on a second sensor signal from second sensor 6. Determiner 3 calculates a brightness change value indicating a difference between brightness of image data generated by first sensor 5 through image capturing at a predetermined timing and brightness of image data generated by first sensor 5 through image capturing after the predetermined timing. In the first determination mode, determiner 3 suspends determination as to whether a person is present if the brightness change value is greater than a predetermined value, and determines whether a person is present if the brightness change value is less than the predetermined value.

Load control device 10 according to the present embodiment achieves higher accuracy of detecting a person since determiner 3 suspends determination as to whether a person is present in the first determination mode if the brightness change value is greater than or equal to the predetermined value, and determines whether a person is present if the brightness change value is less than the predetermined value.

The first briefly describes the entirety of load control system 30.

Load control system 30 includes load control devices 10, switch 31, lighting apparatuses 32, transmitter 33, and power transformer 35, as illustrated in FIG. 7. In load control system 30, plural load control devices 10, switch 31, plural lighting apparatuses 32, and transmitter 33 are electrically connected to one another via transmission line 30 a. In load control system 30, power transformer 35 and load control devices 10 are electrically connected to one another via power source line 30 b.

Switch 31 is configured to control turning on and off and dimming lighting apparatuses 32. Switch 31 is configured to transmit control signals for turning on and off and dimming lighting apparatuses 32, via transmitter 33 by multiplexing. Switch 31 can control turning on and off and dimming certain lighting apparatus 32 only, among plural lighting apparatuses 32, by transmitting a control signal by multiplexing. The control signal includes address information which identifies lighting apparatus 32 which is to be controlled and control information for controlling lighting apparatus 32. In other words, load control system 30 is configured to transmit a control signal through two-wire transmission line 30 a by multiplexing.

Lighting apparatuses 32 each include remote control relay 32 a, relay control terminal unit 32 b, and dimming terminal unit 32 c. In the following, relay control terminal unit 32 b is referred to as relay controller 32 b, and dimming terminal unit 32 c is referred to as dimmer 32 c. Relay controller 32 b controls remote control relay 32 a in response to a control signal from transmitter 33. Relay controller 32 b has an address determined for the controller. Relay controller 32 b controls remote control relay 32 a, based on the content of a control signal which includes address information indicating the same address as the address predetermined for the controller, among the control signals transmitted by multiplexing. Remote control relay 32 a includes a contact for switching between on and off of lighting apparatus 32. Remote control relay 32 a switches between on and off of lighting apparatus 32, based on an indication from relay controller 32 b. Dimmer 32 c has an address determined for the dimmer. Dimmer 32 c extracts a control signal which includes address information indicating the same address as the address predetermined for the dimmer, among the control signals transmitted by multiplexing. Dimmer 32 c controls the dimming of lighting apparatus 32, based on the content of the control signal. Lighting apparatus 32 functions as a lighting apparatus having a communication function, which includes remote control relay 32 a, relay controller 32 b, and dimmer 32 c.

Transmitter 33 is configured to transmit various control signals to plural lighting apparatuses 32 through two-wire transmission line 30 a. Transmitter 33 includes a transmission circuit which transmits a control signal. Transmitter 33 is configured to prevent interference of control signals from plural load control devices 10, and transmit the control signals to lighting apparatuses 32. Single transmitter 33 is configured to control, by the transmitter itself, 256 circuits of load devices, for example. Power transformer includes a transformer which changes a voltage of commercial alternating current power to a predetermined voltage, for example. Power transformer 35 supplies load control devices 10 with power for driving load control devices 10. Load control system 30 may include a lighting controller which controls plural lighting apparatuses 32. The lighting controller turns lighting apparatuses 32 on and off by controlling lighting apparatuses 32 in conjunction with load control devices 10, for instance.

The following describes basic operation of load control device 10 in load control system 30.

For example, if load control device 10 determines, based on a first sensor signal from first sensor 5 and a second sensor signal from second sensor 6, that a person is staying in the detection range of load control device 10 while lighting apparatus 32 is on, load control device 10 maintains lighting apparatus 32 on. If load control device 10 is to maintain certain lighting apparatus 32 on, load control device 10 may output, from communicator 4, a control signal for maintaining lighting apparatus 32 on, or may not output a control signal. Load control device 10 outputs, from communicator 4, a control signal for diming certain lighting apparatus 32 if determiner 3 determines that a person is moving out of the detection range of load control device 10, based on both a first sensor signal and a second sensor signal. Dimming of lighting apparatus 32 is controlled based on a control signal which includes address information indicating the same address as the address predetermined for dimmer 32 c of the lighting apparatus. If load control device 10 determines that a person is moving out of the detection range of load control device 10, load control device dims, for example, certain lighting apparatus 32 in the on state with 100% output to 50% output.

If load control device 10 determines that a person is not present, based on a first sensor signal from first sensor 5 and a second sensor signal from second sensor 6, for example, load control device 10 outputs, from communicator 4, a control signal for turning off certain lighting apparatus 32. Relay controller 32 b of certain lighting apparatus 32 controls remote control relay 32 a, based on a control signal which includes address information indicating the same address as the address predetermined for relay controller 32 b. Remote control relay 32 a turns off lighting apparatus 32, based on an indication from relay controller 32 b. In load control system 30 which includes load control devices 10 according to the present embodiment, a load device which is a control target controlled by load control device 10 is lighting apparatus 32. Examples of the control target include not only lighting apparatus 32, but also various load devices such as a ventilation fan and an air conditioner.

The following describes a specific structure of load control device 10.

Casing 1 of load control device 10 includes a bottom plate and cylinder 1 b. Casing 1 has a cylindrical shape with a closed end, which is formed by the bottom plate and cylinder 1 b, as illustrated in FIG. 2. Lid 2 includes bottom portion 2 a and cylinder portion 2 b. Lid 2 has a cylindrical shape with a closed end, which is formed by bottom portion 2 a and cylinder portion 2 b. In a state where casing 1 and lid 2 are fitted, load control device 10 forms a box which is hollow inside. Load control device 10 has a cylindrical shape, in a state where casing 1 and lid 2 are fitted. Casing 1 has a pair of through holes 1 ca in the circumferential portion in plan view. Casing 1 has a structure in which first screws inserted in through holes 1 ca are tightened in screw holes of lid 2. Casing 1 can be formed using electrically insulating resin material such as urea resin, for example. Lid 2 can be formed using electrically insulating resin material, such as urea resin, for example. Casing 1 and lid 2 may be formed using the same material or different materials.

Lid 2 has first window hole 2 aa and second window holes 2 ab. Lid 2 has one first window hole 2 aa in the center portion of bottom portion 2 a. First window hole 2 aa passes through bottom portion 2 a in the thickness direction of bottom portion 2 a. The central axis of first window hole 2 aa is in the direction perpendicular to outer bottom surface 2 ca of bottom portion 2 a. First window hole 2 aa has a circular shape in plan view. Lid 2 has four second window holes 2 ab around first window hole 2 aa. The central axis of second window holes 2 ab is inclined outward relative to the line perpendicular to outer bottom surface 2 ca of bottom portion 2 a. Outer bottom surface 2 ca of bottom portion 2 a has depressed portions 2 da around second window holes 2 ab, which are stretching outward. Lid 2 has, on the bottom portion 2 a side, flange portion 2 c protruding outward from the outer circumference of cylinder portion 2 b.

Load control device 10 includes plate 12 which covers outer bottom surface 2 ca of lid 2. Plate 12 has a circular shape. Plate 12 has first opening 12 a in the center portion corresponding to first window hole 2 aa. Plate 12 has second openings 12 b in the circumferential portion corresponding to second window holes 2 ab. Plate 12 has hollows 12 da around second openings 12 b in the circumferential portion corresponding to depressed portions 2 da. Plate 12 serves as a face plate of load control device 10. First sensor 5 of load control device 10 is exposed from first opening 12 a of plate 12. Second sensors 6 of load control device 10 are exposed from second openings 12 b of plate 12.

First sensor 5 includes lens part 5 b, lens holder 5 c, and cover plate 5 d, in addition to imaging element 5 a. For example, a solid state imaging element such as a complementary metal oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor can be used as imaging element 5 a. Imaging element 5 a is configured so as to obtain image data. Lens part 5 b is provided in front of imaging element 5 a. Lens part 5 b includes, for example, a lens which condenses light, and an adjuster which relatively displaces imaging element 5 a and the lens. The adjuster can be formed using a permanent magnet which holds the lens, and a magnet coil which moves the permanent magnet. Lens part 5 b moves the lens by adjusting a current flowing through a coil, thus adjusting a focal point with respect to imaging element 5 a. Lens holder 5 c holds lens part 5 b. Lens holder 5 c has a ring shape. Cover plate 5 d is provided so as to close third opening 5 c 1 of ring-shaped lens holder 5 c. Cover plate 5 d is disposed in front of lens part 5 b. Cover plate 5 d is light-transmissive. Cover plate 5 d is colored, thus making it difficult to see inside of first sensor 5 from the outside. Lens holder 5 c includes indicator 8 at a portion of the ring shape in plan view. Indicator 8 has at least one light emitting diode 8 a. Light emitting diode 8 a shows the operating state of load control device 10, based on the color of emitted light and the illumination state of the diode.

Second sensors 6 each include sensor cover 6 b, in addition to infrared sensor 6 a. Infrared sensor 6 a has a cylindrical shape. Infrared sensor 6 a has three terminals 6 a 1 protruding in the axial direction. Sensor cover 6 b has tube portion 6 b 1 and dome portion 6 b 2. Tube portion 6 b 1 has a cylindrical shape. Dome portion 6 b 2 covers tube portion 6 b 1. Dome portion 6 b 2 has a lens which condenses infrared radiation. Tube portion 6 b 1 and dome portion 6 b 2 of sensor cover 6 b are integrally formed. Sensor cover 6 b can be formed using polyethylene resin, for example. Sensor cover 6 b covers infrared sensor 6 a on the side opposite to terminals 6 a 1. In second sensor 6, infrared sensor 6 a detects, through sensor cover 6 b, infrared radiation emitted by a person. In order to secure a predetermined viewing angle, second sensor 6 has sensor cover 6 b protruding outward relative to outer bottom surface 2 ca of lid 2.

Second sensors 6 are mounted on first circuit board 13 a via lid 2. FIG. 2 illustrates that second sensors 6 are directly mounted on first circuit board 13 a, to facilitate a description. First circuit board 13 a has a disc-like shape in plan view. First circuit board 13 a includes first insertion holes 13 b and second insertion holes 13 c. First insertion holes 13 b are formed into an arc shape in plan view. First insertion holes 13 b are each formed to house a part of tube portion 6 b 1 of sensor cover 6 b. Infrared sensors 6 a are disposed so as to be partially in contact with first circuit board 13 a. Terminals 6 a 1 of infrared sensors 6 a are inserted in second insertion holes 13 c. First circuit board 13 a has three second insertion holes 13 c for each second sensor 6. Second insertion holes 13 c are each formed into an oval in plan view. Terminals 6 al are inserted in second insertion holes 13 c, being inclined relative to first surface 13 aa of first circuit board. 13 a. First insertion holes 13 b and second insertion holes 13 c of first circuit board 13 a allow infrared sensors 6 a to be mounted, infrared sensors 6 a being inclined relative to first surface 13 aa of first circuit board 13 a. Infrared sensors 6 a each have a light-receiving surface for receiving infrared radiation, and an optical axis that is inclined toward the circumference from the center portion of lid 2 in plan view, the optical axis being perpendicular to the light-receiving surface.

On first surface 13 aa of first circuit board 13 a, electronic device 5 j such as a field-programmable gate array (FPGA) is mounted, in addition to imaging element 5 a, light emitting diode 8 a, and infrared sensors 6 a. Mounting components such as an integrated circuit (IC) and a microcomputer are mounted on a second surface of first circuit board 13 a opposite first surface 13 aa. Wiring is formed into a predetermined shape on first circuit board 13 a so as to establish electrical connection with imaging element 5 a, light emitting diode 8 a, infrared sensors 6 a, electronic device 5 j, and various mounting components. In load control device 10, determiner 3 and communicator 4 are achieved using electronic device 5 j and such mounting components. First circuit board 13 a is fixed to lid 2 with screws.

First circuit board 13 a is electrically connected with second circuit board 13 f. Second circuit board 13 f has a disc-like shape. Various electronic components 13 e are mounted on second circuit board 13 f. Examples of electronic components 13 e include an electrolytic condenser, a photocoupler, a thermo sensitive register, a transistor, a varistor, and a diode. Second circuit board 13 f forms a direct current-direct current (DC-DC) converter, using various electronic components 13 e mounted thereon. Second circuit board 13 f forms a power supply circuit which supplies power to first circuit board 13 a. Second circuit board 13 f is fixed to casing 1 with second screw 13 d. Second circuit board 13 f includes plural terminals. In load control device 10, plural terminals are exposed on a side of casing 1 opposite lid 2. The terminals can function as feed terminals which supply power to load control device 10. The terminals can function as communication terminals which transmit control signals from communicator 4.

Load control device 10 includes tightening screw 10 d and metal clip fitting 10 e. Tightening screw 10 d is provided along groove 10 m along casing 1 and lid 2. Metal clip fitting 10 e is formed so as to allow tightening screw 10 d to be fit in the metal clip fitting. Load control device 10 is attached to installation surface 30 ca of, for instance, ceiling material 30 c of a building, as illustrated in FIG. 5. Load control device 10 is disposed, being embedded in through port 30 cb provided in ceiling material 30 c. Flange portion 2 c is formed so as to be in contact with installation surface 30 ca in a state where load control device 10 is embedded in through port 30 cb in ceiling material 30 c. Flange portion 2 c and metal clip fitting 10 e attach load control device 10 into ceiling material 30 c using tightening screw 10 d and metal clip fitting 10 e. Load control device 10 is disposed being attached into ceiling material 30 c so that first sensor 5 and second sensors 6 detect a space vertically below construction surface 30 ca.

The following describes the circuit configuration of load control device with reference to FIG. 4.

Load control device 10 includes power supply 7, in addition to determiner 3, communicator 4, first sensor 5, and second sensors 6. Power supply 7 is achieved by the DC-DC converter formed on second circuit board 13 f. Power supply 7 supplies power to determiner 3, communicator 4, first sensor 5, and second sensors 6.

Determiner 3 includes controller 3 s and timer 3 t. Determiner 3 receives a first sensor signal from first sensor 5 and second sensor signals from second sensors 6. Controller 3 s is configured to cause communicator 4 to output, based on a first sensor signal and a second sensor signal, a control signal for controlling turning on and off and dimming lighting apparatus 32. Controller 3 s can be achieved by, for example, a microcomputer in which a central processing unit (CPU), for instance, is used. Timer 3 t measures time. Communicator 4 outputs various control signals, based on indications from determiner 3. Communicator 4 is configured to transmit a control signal by multiplexing.

Controller 3 s causes communicator 4 to output a control signal for turning off lighting apparatus 32 after a predetermined time period measured by timer 3 t has elapsed since controller 3 s has determined that a person is not present, based on a first sensor signal and a second sensor signal. Controller 3 s resets the counting by timer 3 t if controller 3 s determines, based on a first sensor signal and a second sensor signal, that a person is present while timer 3 t is measuring time. Load control device 10 can maintain lighting apparatus 32 on until timer 3 t completes decrementing time newly after the counting is reset.

First sensor 5 includes image processor 5 e, in addition to imaging element 5 a. Image processor 5 e includes arithmetic controller 5 f, first storage 5 g, and second storage 5 h. Arithmetic controller 5 f performs arithmetic processing on image data generated by imaging element 5 a through image capturing. Arithmetic controller 5 f is achieved using a FPGA and a digital signal processor (DSP). A semiconductor element which can perform digital image processing at high speed, such as an advanced image processor, may be used for arithmetic controller 5 f, instead of the DSP.

First storage 5 g stores image data generated by imaging element 5 a through image capturing. A mass storage device is used for first storage 5 g so that high volume image data can be stored. For example, a volatile memory having comparatively large storage capacity such as dynamic random access memory (DRAM) can be used for first storage 5 g. Second storage 5 h stores in advance shape data indicating contours of a person viewed from the ceiling material 30 c side, for instance. Shape data indicating contours of a person is used to perform image discrimination processing for distinguishing between a person and an object other than a person. Second storage 5 h is included separately from first storage 5 g. A non-volatile memory such as synchronous DRAM (SDRAM) is used for second storage 5 h so as to transfer shape data at a comparatively high speed.

Image processor 5 e temporarily stores into first storage 5 g image data generated by imaging element 5 a through image capturing. Image processor 5 e reads image data stored in first storage 5 g into arithmetic controller 5 f, as appropriate. Image processor 5 e reads shape data indicating contours of a person from second storage 5 h into arithmetic controller 5 f, as appropriate. Arithmetic controller 5 f performs image differentiation processing on the read image data. In the image differentiation processing, as a difference in the background, a current image based on current image data captured by imaging element 5 a is compared with a background image based on background data captured in advance by imaging element 5 a before a person enters first detection range 10 aa. Background data may be stored in first storage 5 g or in second storage 5 h. Arithmetic controller 5 f compares a current image with a background image, and generates a differential image based on a difference per pixel. In the image differentiation processing, a differential image may be generated based on a temporal difference obtained by comparing two image data that are read by imaging element 5 a at different times, rather than based on a difference in background. Arithmetic controller 5 f performs processing for extracting differential pixels from a differential image obtained by comparing a current image with a background image and binarizing luminance values. In the processing for extracting differential pixels, a luminance value of a pixel which does not change between a current image and a background image is below a predetermined threshold. In the processing for extracting differential pixels, if a person is present, there is a change between a current image and a background image. In the processing for extracting differential pixels, a luminance value of a pixel which changes between a current image and a background image is greater than or equal to a predetermined threshold.

Arithmetic controller 5 f performs processing for extracting differential pixels, and thereafter performs recognition processing on the differential pixels. In the recognition processing, image discrimination processing by shape pattern recognition for determining how much a shape of a contour formed by a group of the extracted differential pixels matches shape data indicating a contour of a person prestored in second storage 5 h. Arithmetic controller 5 f can determine whether the shape of the extracted contour corresponds to a person or not, by determining a percentage at which the shape of the extracted contour matches prestored shape data indicating a contour of a person. Arithmetic controller 5 f can extract the contour shape using, for example, a Sobel filter, a Prewit filter, or the like, as recognition processing on the differential pixels.

Arithmetic controller 5 f outputs a first sensor signal indicating that a person is present, upon the detection of presence of a person by image discrimination processing. Each time imaging element 5 a outputs image data, first sensor 5 compares image data with a background image, thus appropriately detecting whether a person is present. Load control device 10 can detect whether a person is present even if only one person who is not moving is present.

Infrared sensor 6 a of each of second sensors 6 includes pyroelectric element 6 d and signal processing circuit 6 e. Pyroelectric element 6 d detects infrared radiation emitted by a person. Signal processing circuit 6 e includes amplifier circuit 6 f, band-pass filter 6 g, comparator circuit 6 h, and output circuit 6 j. Amplifier circuit 6 f amplifies a signal from pyroelectric element 6 d. Band-pass filter 6 g eliminates an unnecessary frequency component which can result in noise, from the amplified signal. Comparator circuit 6 h determines whether a signal from which an unnecessary frequency component has been eliminated exceeds a predetermined threshold. If the signal exceeds the predetermined threshold, output circuit 6 j outputs a second sensor signal indicating that a person is present. Specifically, signal processing circuit 6 e amplifies a signal from pyroelectric element 6 d, and compares the amplified signal with the threshold. Infrared sensor 6 a outputs a second sensor signal via terminals 6 a 1 to determiner 3 if the signal from pyroelectric element 6 d is greater than the threshold.

Load control device 10 determines whether a person is present, based on a first detection signal from first sensor 5 and second detection signals from second sensors 6, and controls turning on and off and dimming lighting apparatuses 32 individually. In particular, first sensor 5 detects whether a person is present, based on a difference of image data, and thus load control device 10 can determine whether a person is in first detection range 10 aa and determine that a person has moved out of first detection range 10 aa. Load control device 10 can dim lighting apparatus 32 while a person is passing through first detection range 10 aa, and turns on lighting apparatus 32 only when a person stays in first detection range 10 aa.

First sensor 5 detects whether a person is present, based on image data generated by imaging element 5 a through image capturing. First detection range 10 aa needs to have predetermined brightness to allow imaging element 5 a of first sensor 5 to obtain image data. Infrared sensors 6 a detect whether a person is present, based on infrared radiation emitted by a person, and thus second sensors 6 can detect whether a person is present, independently of brightness.

In load control device 10, first sensor 5 obtains image data at predetermined time intervals. Load control device 10 can detect the brightness around the load control device, using first sensor 5. First sensor 5 calculates, as ambient brightness, an illuminance from an average value of the entire image data generated by imaging element 5 a through image capturing. In other words, first sensor 5 also functions as an illuminance sensor. If the brightness detected by first sensor 5 is greater than a predetermined illuminance, determiner 3 operates in the first determination mode to determine whether a person is present, based on a first sensor signal and a second sensor signal. A threshold of the predetermined illuminance can be set to 20 lx, for example, although this value depends on image capturing performance of imaging element 5 a. The threshold of illuminance can be stored in second storage 5 h, for example.

If the ambient brightness around load control device 10 is less than the predetermined illuminance, determiner 3 operates in the second determination mode to determine, based only on a second sensor signal from second sensor 6, whether a person is present. Determiner 3 causes communicator 4 to output a control signal, based on the result of determination in the second determination mode. Independently of the ambient brightness, load control device 10 may determine, based on a first detection signal and a second detection signal, whether a person is present, and output a control signal from communicator 4.

The following briefly describes first detection range 10 aa and second detection ranges 10 ba of load control device 10 according to the present embodiment.

For example, first detection range 10 aa is formed in a quadrangular pyramid having first sensor 5 as a vertex, as illustrated in FIG. 5. Second detection range 10 ba is formed in an oblique circular cone having second sensor 6 as a vertex. FIG. 5 illustrates second detection range 10 ba where one of four second sensors 6 detects presence of a person, as an example. On the floor, first detection range 10 aa of first sensor 5 is formed in a rectangular shape. Second detection range 10 ba of second sensor 6 is formed into an oval shape on the floor so as to overlap first detection range 10 aa of first sensor 5. First sensor 5 and second sensors 6 are disposed such that the longitudinal direction of each of second detection ranges 10 ba on the floor is along a diagonal line of first detection range 10 aa on the floor. Load control device 10 is disposed such that the entirety of four second detection ranges 10 ba includes first detection range 10 aa on the floor.

First sensor 5 can be configured to switch between on and off of the detection function of detecting whether a person is present, for each of a plurality of regions into which first detection range 10 aa is divided. Load control device 10 can turn off, in advance, the detection function in a specific region where detection of presence of a person is not necessary, such as a region where a pillar, for example, is present, depending on where load control device 10 is disposed. First sensor 5 can store the regions into second storage 5 h. Load control device 10 may have a configuration in which divided regions are appropriately determined from the outside using a remote-control device.

Each of the regions overlaps at least one of second detection ranges 10 ba of second sensors 6. When load control device 10 controls, for each of the regions, whether to turn on or off the detection function in the region, load control device 10 turns on or off the detection function in the region which is superposed on at least one of second detection ranges 10 ba of second sensors 6. Once load control device 10 turns off the detection function in a region, load control device 10 does not detect a person even if a person is present in the region in which the detection function is off.

In load control device 10, if a region in which the detection function is off overlaps second detection range 10 ba, first sensor 5 does not detect whether a person is present, whereas second sensor 6 detects whether a person is present. If the ambient brightness is sufficient, load control device 10 determines whether a person is present, based on a logical product of a first sensor signal and a second sensor signal, which is the determination in the first determination mode. If the ambient brightness is greater than the predetermined illuminance, determiner 3 performs signal processing based on a logical product of a first sensor signal and a second sensor signal, thus determining whether a person is present. Yet, determiner 3 does not determine that a person is present even if second sensor 6 detects presence of a person in a region in which the detection function of first sensor 5 is off.

If the ambient brightness is insufficient, load control device 10 determines whether a person present, based on only a second sensor signal from second sensor 6, which is the determination in the second determination mode. For each of regions into which first detection range 10 aa of first sensor 5 is divided, according to whether the detection function is on or off in the region, controller 3 s of load control device 10 automatically controls on and off of second sensor 6 which detects presence of a person in second detection range 10 ba that overlaps the region, when load control device 10 determines regions. If controller 3 s sets the detection function in certain region to off, load control device 10 can control and turn off the function of second sensor 6 corresponding to the region in which the detection function is set to off. If controller 3 s sets the detection function in a certain region to off, load control device 10 may turn off second sensor 6 corresponding to the region in which the detection function is set to off, by negating a second sensor signal from second sensor 6. Thus, load control device 10 may control on and off of second sensor 6 by controlling the power supply to second sensor 6 or by determiner 3 asserting or negating a second sensor signal from second sensor 6.

The following describes operation of determiner 3 of load control device 10.

Load control device 10 detects ambient brightness by detecting an illuminance using imaging element 5 a, and determiner 3 automatically switches between the first determination mode and the second determination mode.

Load control device 10 obtains predetermined image data by first sensor 5 adjusting exposure. Exposure can be adjusted by moving the lens of lens part 5 b, for example. It takes certain time for first sensor 5 to adjust exposure. Load control device 10 may be unable to obtain accurate image data until first sensor 5 finishes exposure adjustment, if lighting apparatus 32 is turned on and consequently the ambient brightness suddenly changes, for example. First sensor 5 may incorrectly detect or not detect presence of a person due to overexposure/underexposure caused by inaccurately adjusted exposure. In the first determination mode, determiner 3 of load control device according to the present embodiment suspends determination as to whether a person is present if the brightness change value of image data is greater than the predetermined value, and determines whether a person is present if the brightness change value of image data is less than the predetermined value.

FIG. 6 illustrates, in time sequence, on and off (illuminating and not illuminating) of lighting apparatus 32, on and off of the determination function of determiner 3 in the first determination mode, and the determination modes of determiner 3. For example, if lighting apparatus 32 is turned on at time t₁, and consequently the ambient brightness is increased so that determiner 3 of load control device 10 is placed into the first determination mode, the brightness change value of image data is greater than the predetermined value. The brightness change value of image data can be calculated by time differentiation of the illuminance of image data generated by first sensor 5 through image capturing at a predetermined timing and the illuminance of image data generated by first sensor 5 through image capturing at the next timing. The brightness change value of image data can be calculated by arithmetic controller 5 f performing arithmetic processing. Arithmetic controller 5 f determines the magnitude of the brightness change value, based on the predetermined value for determining the magnitude of the brightness change value, which is prestored in second storage 5 h. Determiner 3 suspends determination as to whether a person is present until time t₂ if the brightness change value of image data is greater than the predetermined value. In a state where ambient brightness considerably changes, determiner 3 may invalidate a first detection signal from first sensor 5. Determiner 3 determines whether a person is present after time t₂, based on a first sensor signal and a second sensor signal. Note that determiner 3 may switch from the second determination mode to the first determination mode at time t₂.

Next, the brightness change value of image data may be greater than the predetermined value when lighting apparatus 32 is turned off at time t₃, and consequently the ambient brightness lowers, but determiner 3 is still in the first determination mode. If the brightness change value of image data is greater than the predetermined value, determiner 3 suspends determination as to whether a person is present until time t₄. Determiner 3 determines whether a person is present, based on a first sensor signal and a second sensor signal, after time t₄.

Next, if lighting apparatus 32 is turned on at time t₅ and consequently the ambient brightness increases, and the brightness change value of image data is greater than the predetermined value in the first determination mode as with time t₁, load control device 10 suspends determination as to whether a person is present until time t₆. After time t₆, determiner 3 determines whether a person is present, based on a first sensor signal and a second sensor signal.

Next, for example, if lighting apparatus 32 is turned off at time t₇, and consequently the ambient brightness lowers so that determiner 3 is placed into the second determination mode, load control device 10 determines whether a person is present, only based on a second sensor signal from second sensor 6 even if the brightness change value of image data is greater than the predetermined value. Furthermore, load control device 10 determines whether a person is present, based on a first sensor signal and a second sensor signal when, for example, lighting apparatus 32 is turned off at time t₇, but the ambient brightness does not considerably lower so that the first determination mode is maintained.

Load control device 10 achieves further higher accuracy of detecting a person since determiner 3 suspends determination as to whether a person is present if the ambient illuminance considerably changes and the brightness change value is greater than the predetermined value, whereas determiner 3 determines whether a person is present if the brightness change value is less than the predetermined value.

The following describes operation of determiner 3 to switch between the first and second determination modes and to suspend determination as to whether a person is present in the first determination mode.

FIG. 8 is a flowchart illustrating an example of switching between the first determination mode and the second determination mode by determiner 3 according to the embodiment.

In FIG. 8, determiner 3 determines whether ambient brightness B1 is greater than threshold Th1 (S81), and if determiner 3 determines that B1 is greater, determiner 3 is placed into the first determination mode (S82), and executes determination in the first determination mode (S83). The determination in the first determination mode is to determine whether a person is present, based on the results of detection by both first sensor 5 and second sensor 6. Threshold Th1 may be, for example, brightness corresponding to the lower limit of the brightness range which allows first sensor 5 to capture an image (or to detect a person).

Furthermore, if determiner 3 determines that ambient brightness B1 is not greater than the threshold, determiner 3 is placed into the second determination mode (S84), and executes determination in the second determination mode (S85). The determination in the second determination mode is to determine whether a person is present based on the result of detection by second sensor 6, instead of first sensor 5.

Note that processing as illustrated in FIG. 8 is repeatedly executed at all times or is repeatedly executed at intervals which a person perceives as continuous.

The following describes an example of suspending determination in the first determination mode.

FIG. 9 is a flowchart illustrating an example of suspending determination in the first determination mode by determiner 3 according to the present embodiment.

In FIG. 9, determiner 3 determines whether change value C1 indicating a change in brightness during a certain time period is greater than the predetermined value (S91). If determiner 3 determines that C1 is greater, determiner 3 suspends determination in the first determination mode (S92), and when a predetermined time period has elapsed from when determiner starts suspending the determination (YES in S93), determiner 3 resumes the determination (S94). The certain time period and the change value as mentioned above correspond to a considerable change in brightness which may cause exposure failure of the first sensor. A considerable change in brightness is caused when, for example, lighting apparatus 32 is turned on in a completely dark place with lighting apparatus 32 off or lighting apparatus 32 which is on is turned off and it suddenly becomes completely dark.

According to the example of processing in FIG. 9, malfunction of the first sensor (in other words, incorrectly detecting or not detecting a person) can be inhibited when a considerable change in brightness occurs in the first determination mode, thus further increasing the detecting accuracy.

Note that determiner 3 in FIG. 4 may be achieved as a sensor control device separate from the first sensor and the second sensor. Furthermore, the sensor control device, the first sensor, and the second sensor may constitute one sensor system.

As described above, the sensor control device according to an aspect of the present embodiment is a sensor control device which controls: a first sensor which detects, based on a captured image, whether a person is present in a first detection range; and a second sensor which detects, based on infrared radiation, whether a person is present in a second detection range which overlaps at least a portion of the first detection range, the sensor control device including a determiner which has a first determination mode for determining whether a person is present, based on a result of detection by the first sensor and a result of detection by the second sensor, and a second determination mode for determining whether a person is present, based on a result of detection by the second sensor, wherein the determiner suspends determination as to whether a person is present in the first determination mode, if a brightness change value indicating a change in brightness in the first detection range during a certain time period is greater than a predetermined value in the first determination mode, and determines whether a person is present in the first determination mode, if the brightness change value in the first detection range is less than the predetermined value in the first determination mode.

Here, in the first determination mode, the determiner may determine that a person is present if the first sensor and the second sensor detect presence of the person, and may determine that no person is present if at least one of the first sensor and the second sensor does not detect presence of a person.

Here, in the second determination mode, the determiner may determine that a person is present if the second sensor detects presence of the person, and may determine that no person is present if the second sensor does not detect presence of a person.

Here, the determiner may determine whether a person is present in the first determination mode or the second determination mode, after a predetermined period has elapsed from when the determiner starts suspending the determination as to whether a person is present.

Here, the determiner may switch between the first determination mode and the second determination mode, based on the brightness in the first detection range.

Here, the determiner may switch from the first determination mode to the second determination mode if the brightness change value indicating the change in brightness in the first detection range is greater than the predetermined value and the brightness in the first detection range is lower than predetermined brightness.

Here, the brightness change value may indicate an increase in brightness.

The sensor system according to an aspect of the present embodiment is a sensor system including: the sensor control device; the first sensor; and the second sensor.

Here, a plurality of second sensors may be disposed around the first sensor, the plurality of second sensors each being the second sensor.

The load control system according to an aspect of the present embodiment is a load control system including: the sensor control device; and a controller which controls a load, based on a result of determination by the sensor control device.

While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings. 

What is claimed is:
 1. A sensor control device which controls: a first sensor which detects, based on a captured image, whether a person is present in a first detection range; and a second sensor which detects, based on infrared radiation, whether a person is present in a second detection range which overlaps at least a portion of the first detection range, the sensor control device comprising: a determiner which has a first determination mode for determining whether a person is present, based on a result of detection by the first sensor and a result of detection by the second sensor, and a second determination mode for determining whether a person is present, based on a result of detection by the second sensor, wherein the determiner suspends determination as to whether a person is present in the first determination mode, if a brightness change value indicating a change in brightness in the first detection range during a certain time period is greater than a predetermined value in the first determination mode, and determines whether a person is present in the first determination mode, if the brightness change value in the first detection range is less than the predetermined value in the first determination mode.
 2. The sensor control device according to claim 1, wherein in the first determination mode, the determiner determines that a person is present if the first sensor and the second sensor detect presence of the person, and determines that no person is present if at least one of the first sensor and the second sensor does not detect presence of a person.
 3. The sensor control device according to claim 1, wherein in the second determination mode, the determiner determines that a person is present if the second sensor detects presence of the person, and determines that no person is present if the second sensor does not detect presence of a person.
 4. The sensor control device according to claim 1, wherein the determiner determines whether a person is present in the first determination mode or the second determination mode, after a predetermined period has elapsed from when the determiner starts suspending the determination as to whether a person is present.
 5. The sensor control device according to claim 1, wherein the determiner switches between the first determination mode and the second determination mode, based on the brightness in the first detection range.
 6. The sensor control device according to claim 5, wherein the determiner switches from the first determination mode to the second determination mode if the brightness change value indicating the change in brightness in the first detection range is greater than the predetermined value and the brightness in the first detection range is lower than predetermined brightness.
 7. The sensor control device according to claim 1, wherein the brightness change value indicates an increase in brightness.
 8. A sensor system comprising: the sensor control device according to claim 1; the first sensor; and the second sensor.
 9. The sensor system according to claim 8, wherein a plurality of second sensors are disposed around the first sensor.
 10. A load control system comprising: the sensor control device according to claim 1; and a controller which controls a load, based on a result of determination by the sensor control device. 